Minho took Thomas to a secret house, inside the room they built a giant and very detailed maze with wood sticks. Minho told Thomas they thought there’s no exit of the maze before Thomas came because he walked in the maze for 3 years he knows the pattern of how it will change at night and remembered all the roads but just couldn’t find the exit of it.
People are afraid of the griever they are scared to know what they look like and fight against them. If they killed one of it early together they could get out from the maze before those scientists send Thomas here.
People’s memories were erased before they were sent into the maze. If their memories weren’t erased I guess they will be smarter and braver and will easily find out the entrance of the griever is their exit.
Wicked doesn’t want them to get out from the maze with a short period of time, they erased their memories because if they knew their home was destroyed I think people would rather stay in the maze than trying to escape.